Sarcomas are complex tissues that are comprised of both cancer cells and normal cells, as well as extracellular matrix. Crosstalk and collaboration among all components of the tumor is necessary for local tumor growth as well as metastasis to distant sites. Importantly, our research has shown that Ewing sarcoma tumor cells are very dynamic and they change phenotype rapidly in response to signals from their microenvironment. It is clear from our studies, as well as others, that these changes in cancer cell phenotype contribute to the tumor heterogeneity that drives disease relapse, metastasis, and emergence of drug resistant disease. Using diverse tumor model systems and state-of-the-art genomic, epigenomic, and functional assays, we are elucidating the molecular mechanisms that cause tumor cells to change states.
Our most recent work has focused on tumor microenvironment crosstalk and how Wnt/beta-catenin and TGF-beta signaling in discrete tumor-cell subpopulations collaborate to alter the local extracellular matrix, promoting tumor angiogenesis and disease progression.
Ewing sarcomas are characterized by the presence of gene fusions, most commonly EWS-FLI1, often without evidence of any other gene mutations. As such, changes in cell phenotype that promote metastatic progression are largely driven by non-genetic mechanisms. We are studying how disruption of normal epigenetic regulation of developmental programs leads to tumor initiation and tumor progression. In particular, we are focused on how epigenetic hijacking of developmental transcription factors such as HOX genes leads to malignant transformation of normal stem cells. In addition, we are studying how these processes work in established sarcoma cells to switch chromatin states allowing cells to adapt to new environments and to stress. Understanding the fundamental biology of epigenetic processes in Ewing sarcoma will lead to new treatment strategies that employ less toxic, tumor-targeted drugs (i.e. inhibitors of bromodomain proteins, HDACs, menin, and other epigenetic modifying agents).
The process of rapid proliferation and tumor expansion exposes tumor cells to multiple sources of internal and external stress. Tumor cells have adapted ways to maintain cellular homeostasis that allow them to survive and thrive under conditions that would destroy less resilient cells. Among the most important of these adaptation mechanisms is metabolic reprogramming. By rewiring their metabolic pathways, cancer cells are able to maintain redox and amino acid homeostasis and epigenetic stability, while generating the extra energy and biomaterials that are necessary to sustain their growth. Our current studies of Ewing sarcoma are investigating how serine biosynthesis and amino acid flux contribute to tumor progression. Importantly, these studies have identified critical connections between the epigenome and metabolic reprogramming that we hypothesize are necessary for metastasis.